1. Field of the Invention
The present invention relates to a resin gear that transmits rotative power.
2. Description of the Related Art
Conventionally, a following resin spur gear 106 configured to reduce rotation transmission error and noise is known (refer to Patent Literature 1). As shown in FIG. 16 and FIG. 17, a tooth surface 103 of a two-pair meshing area 102 on a tooth crest 101 side is cut such that a rigidity of a tooth 104 in the two-pair meshing area 102 on the tooth crest side 101 is less than a rigidity of a tooth on a standard involute spur gear (referred to, hereinafter, as a spur gear). Difference between an amount of deformation in a one-pair meshing area 105 of the tooth 104 and an amount of deformation in the two-pair meshing area 102 of the tooth 104 is reduced. Patent Literature 1: Japanese Patent Laid-open Publication No. Heisei 8-312755 (refer, in particular, to FIG. 1 to FIG. 3).
However, when the conventional resin spur gear 106 shown in FIG. 16 and FIG. 17 is used on a driven side, when the resin spur gear 106 and a driving side gear start to mesh, an entire area of the tooth crest 101 in a tooth width direction collides with a tooth root side of a mating gear (driving side gear). Noise resulting from a collision sound between the teeth on the driven side and the teeth on the driving side cannot be sufficiently reduced.
When the conventional resin spur gear 106 shown in FIG. 16 and FIG. 17 is used on the driving side, sliding occurs between the entire area of the tooth crest 101 in the tooth width direction and a tooth surface of the mating gear when the meshing between the resin spur gear 106 and the tooth on the mating gear is released. Generally, a sliding speed of the tooth surface of the spur gear is fastest on the tooth crest side and the tooth root side during rotation transmission. Therefore, when the conventional resin spur gear 106 shown in FIG. 16 and FIG. 17 is used on the driving side, a sliding sound of the tooth 104 is loud when the meshing between the resin spur gear 106 and the tooth on the mating gear is released. Noise resulting from the sliding of the tooth 104 cannot be sufficiently reduced.